Foot and Mouth Disease in Livestock and Reduced Cryptosporidiosis in Humans, England and Wales

William J. Smerdon, Tom Nichols, Rachel M. Chalmers, Hilary Heine, Mark H. Reacher

Disclosures

Emerging Infectious Diseases. 2003;9(1) 

In This Article

Results

The data set comprised 51,322 reports of Crytosporidium. We concluded that an outlying count of 387 reports with a specimen date of October 6, 1995, was a batch-reporting error of cases from a large waterborne outbreak in Torbay, in southwest England, which occurred during July-September 1995[9]. Annual reporting rates varied from 6.7-11/100,000 for England and Wales as a whole. Rates were generally <5/100,000 in London; in several recent years, the highest rates occurred in northwest England ( Table 3 ).

The timing of clearly identifiable spring and autumn peaks of Cryptosporidium laboratory reports was fairly consistent from year to year (Figure 1). Weeks 8-39 of each year included all spring peaks and the first half of all autumn peaks. However, spring and autumn peaks were not always clearly identifiable in each year. The year 1993 was notable for the absence of an autumn peak; in 1996 and 1997, identifying either a spring or autumn peak was difficult (Figure 1). In 2001, weekly counts remained lower than in previous years until approximately week 35, when an autumn peak comparable to previous years was observed (Figure 1).

Laboratory reports of Cryptosporidium species to Public Health Laboratory Service-Communicable Disease Surveillance Centre, by specimen week, England and Wales, 1991-2001. Reporting artifact on October 6, 1995 not shown.

By modeling counts, a significant decrease in overall seasonal and yearly associations was noted only in 1992 and in 2001 ( Table 4 ). Weeks 8-39 in 1992 showed an estimated 22% decrease, whereas weeks 8-39 in 2001, corresponding to the FMD epidemic, showed an estimated 35% (95% confidence interval [CI] 20% to 47%) decrease in England and Wales as a whole (p=0.001). We estimated that the FMD epidemic interval was associated with some reduction of human cryptosporidiosis in all regions of England and in Wales, but the largest association was in northwest England, which showed decrease of approximately 63% (95% CI 31% to 80%) (p=0.001) ( Table 5 ).

The age distribution for persons with reported cryptosporidiosis for weeks 8-39 in 2001 was similar for the same time of year in each of the preceding 10 years. A history of foreign travel preceding diagnosis was given in 5% of reports and showed a single autumn peak in weeks 31-41 of each year, while those reports from case-patients without a history of foreign travel showed both spring and autumn peaks (Figure 2).

Laboratory reports of Cryptosporidium species to Public Health Laboratory Service-Communicable Disease Surveillance Centre, by specimen week, including reports with and without foreign travel, England and Wales, 1991-2001.

Genotyping results were available for approximately half of the reported cases of cryptosporidiosis made to PHLS-CDSC in 2000 and 2001. When specimens from persons with a history of recent foreign travel were excluded, the proportion of genotype 2 cases was generally higher in the first half of both years (Figure 3). In weeks 21-24 of 2001 (May 21-June 17), the proportion of genotype 2 cases was significantly lower than for the same weeks of 2000 (Figure 3). In weeks 8-39 as a whole, the proportion of genotype 2 cases was significantly lower in 2001 than in 2000 (49%, 338/696 in 2001; 63%, 977/1,558 in 2000; p<0.00005).

Laboratory isolates of Cryptosporidium species, proportion of genotype 2, by specimen week, England and Wales, 2000 and 2001.

Mean rainfall in England and Wales between January and June (to approximately week 26) was <60 mm in 1992 and 1996 ( Table 6 ): in these years, the spring peak in Cryptosporidium reporting was also below normal (Figure 1). In contrast, rainfall in the first 6 months of 2001 was above the 1961-1990 average and showed a pattern more like that that observed in 1998, 1999, and 2000: in these years, a spring peak in Cryptosporidium reporting was conspicuous (Figure 1; Table 6 ).

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